The present invention relates to a driving apparatus for transmitting the rotation of a motor, after decelerated by a decelerating mechanism, to a driven device, and more particularly, to a driving apparatus that is equipped with a clutch for preventing the transmission of rotation from a decelerating mechanism to a motor.
A general power window apparatus comprises a driving apparatus equipped with a motor, and a driven device driven by the driving apparatus which moves a windowpane up and down, specifically, a lifting mechanism. The driving apparatus includes an output unit equipped with a worm gear mechanism which functions as a decelerating mechanism. The worm gear mechanism comprises a worm shaft coupled to a rotating shaft of the motor, and a worm wheel meshed with the worm shaft. The rotation of the motor is decelerated by the worm gear mechanism before it is transmitted to the lifting mechanism. In other words, a torque of the motor is amplified by the worm gear mechanism before it is transmitted to the lifting mechanism. The lifting mechanism converts the rotation of the motor to up/down movements of the windowpane.
When external force is applied to the windowpane while the motor is not driven, the external force is transmitted from the windowpane to the motor through the lifting mechanism and the output unit, causing the motor to rotate. Therefore, when external force is applied to the windowpane, the windowpane is allowed to move.
To prevent the movement of the windowpane caused by external force, the driving apparatus is equipped with a clutch. The clutch is located in the middle of a power transmission path between the motor and the lifting mechanism in the output unit. The clutch allows the power of the motor to be transmitted to the lifting mechanism through the output unit. However, when external force is applied to the windowpane, the clutch is locked to make a rotation impossible in order to prevent the external force from moving the lifting mechanism. In other words, the clutch blocks the transmission of rotation from the output unit to the motor.
Conventionally, the clutch is located between the worm wheel of the worm gear mechanism and the lifting mechanism in the output unit. However, in the decelerating mechanism, i.e. the worm gear mechanism functioning as a torque amplifying mechanism, the torque generated by the worm wheel is significantly larger than the torque generated by the worm shaft. Therefore, the clutch positioned between the worm wheel and the lifting mechanism is subjected to a large load. To stand such a large load, the clutch must be formed large in size and have a high strength. This will increase the manufacturing cost of the driving apparatus.
It is an object of the present invention to provide a driving apparatus equipped with a motor and a decelerating mechanism that is capable of reducing the load applied to a clutch.
To achieve the above object, the present invention provides a driving apparatus for driving a driven device. The driving apparatus comprises a motor including a rotating shaft and an output unit coupled to the motor. The output unit comprises a decelerating mechanism for transmitting rotation of the rotating shaft, after decelerating, to the driven device. A clutch is located between the rotating shaft and the decelerating mechanism. The clutch allows the rotation to be transmitted from the rotating shaft to the decelerating mechanism, and blocks the rotation transmitted from the decelerating mechanism to the rotating shaft.
The clutch located between the rotating shaft and the decelerating mechanism is not subjected to a large load. Therefore, the durability required for the clutch can be reduced with a result of a smaller-size clutch.